nixos/nix-ld: Support 32-bit portability

[KoviRobi]

This is for i686-linux only, currently, due to pkgsi686Linux, not sure if there needs to be a more generic pkgs32Bit for e.g. arm 32-bit but perhaps precompiled binaries aren't so widely used on arm.

This improves current state of things anyway.

I have done the formatting in a separate commit so it can be dropped/use a different formatter etc.

I have tested it with some old 32-bit arm GCC (arm-eabi-gcc) that I needed to use for some embedded development.

Cross-referencing

• Support 32 bits applications on 64 bits systems nix-community/nix-ld#28
• 32-bit nix ld nix-community/nix-ld-rs#67

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[zhaofengli]

This is a good start.

Perhaps instead of special variants, this could be structured more generically as programs.nix-ld.systems.<system> where each system attribute is a submodule containing { package = ...; ldso = ...; libraries = ...; }. The existing package and libraries options are passed down to programs.nix-ld.systems.${pkgs.system}. This should make it more composable and support prebuilt binaries for boot.binfmt.emulatedSystems.

In this scheme, we can add support32Bit which would be a convenience shortcut that determines the corresponding 32-bit system (e.g., armv7l-linux), the package set (e.g., pkgsCross.armv7l-hf-multiplatform), and the default libraries to insert.

[KoviRobi]

Thank you, I think I understand what you are saying, I'll have to try it out. I just haven't had the time/energy to do so yet, but it's not abandoned. And yes I think it'll help with non-Intel/AMD architectures e.g. nix-community/nix-ld#27

[KoviRobi]

@zhaofengli I'm sorry I'm struggling to figure out how to do this, I keep running into infinite recursion.

For reference, the builtins.toJSON line gives the following

$ nix build .#test
$ jq < result/etc/foo 
{
  "environment": {
    "ldso": "/nix/store/s76k7qxy3jj6giv2fzmlx5gycdc6ayy7-nix-ld-1.2.3/libexec/nix-ld",
    "pathsToLink": [
      "/share/nix-ld-x86_64-linux"
    ],
    "systemPackages": [
      "/nix/store/46wx8bbsdfb8r21wj6ddb85j4jkjzxc4-ld-library-path"
    ],
    "variables": {
      "NIX_LD_LIBRARY_PATH_x86_64_linux": "/run/current-system/sw/share/nix-ld-x86_64-linux/lib",
      "NIX_LD_x86_64_linux": "/run/current-system/sw/share/nix-ld-x86_64-linux/lib/ld.so"
    }
  },
  "programs": {
    "nix-ld": {
      "systems": {
        "x86_64-linux": {
          "libraries": [
            "/nix/store/rc18a8k50zmrif61250sfidkqvlg41ln-zlib-1.3.1",
            "/nix/store/w6ggciw9mj6r6w332dclhibwmyyv1v67-zstd-1.5.6-bin",
            "/nix/store/3s3rjkl3mx05wp0lmxgwkaqhbz9sy6kk-gcc-13.3.0",
            "/nix/store/did64gsb4sn6xvylw6cswa7697avdrsb-curl-8.8.0-bin",
            "/nix/store/ppfzl2wqzs7ljfj0dxypcvrhr9x6ka3f-openssl-3.0.14-bin",
            "/nix/store/f6vjq8dl0z6x1k7sxvzwnisbncbafnjy-attr-2.5.2-bin",
            "/nix/store/adjqi4kf1k736g7fz23hdqsk39zyjzf8-libssh-0.10.6",
            "/nix/store/wr6x94hzs5ggmpql0qx5j8q2rpfrhm7q-bzip2-1.0.8-bin",
            "/nix/store/iyaxbb5c472akzpbsn3wpmfmh8xzw7k4-libxml2-2.12.7-bin",
            "/nix/store/9xw9hxlmxkjcv02x9d4wrj3sl8gwmkl9-acl-2.3.2-bin",
            "/nix/store/8kd6icdk2025jmvhvxhi6rc3ahhj2qc4-libsodium-1.0.20",
            "/nix/store/kwa0akdagjw0hmv3mam65gmz8f1v8c8k-util-linux-2.39.4-bin",
            "/nix/store/0rlbqq6p9wwb7wbn5vnpck40c76czid3-xz-5.6.2-bin",
            "/nix/store/sbqf71kqhlgaff1ajd8zak09g4wn8ymd-systemd-255.6"
          ]
        }
      }
    }
  }
}

but if I uncomment the # recursive at the bottom of the WIP commit's nix-ld.nix, then I get an infinite recursion, even if I remove the programs.nix-ld.systems.${system}.libraries bit.